Array of sub-aperture refractive elements for steering a light beam

Abstract

The present subject matter includes apparatus and techniques that can be used to reduce losses in systems that perform steering of a light beam. Such steering can be performed in a non-mechanical manner, such as using an electrically-controlled optical structure (e.g., an electro-optical structure). For example, a waveguide can be used to adjust an angle of a light beam (e.g., steer the light beam). The waveguide can include a core, a cladding including an electro-optic material, and electrodes defining an arrangement that, when selectively energized, adjusts an index of refraction of the electro-optic material. In particular, electrode arrangements as described herein can be used to reduce losses, such as losses that would occur due to diffraction.

The invention claimed is: 
     
       1. An apparatus comprising an arrangement of sub-aperture refractive tapered projections for adjusting an angle of a light beam with reduced diffractive losses, the apparatus comprising:
 a first row of the projections, configured to receive light at a first base interconnecting the projections in the first row, and provide refracted light toward a direction of distal peaks of the projections of the first row, wherein an individual one of the sub-projections in the first row includes a planar surface that is configured to refractively adjust an angle of a corresponding sub-aperture portion of the light beam and decrease a size of the corresponding sub-aperture portion of the light beam; and 
 a second row of the projections, configured to receive light from a direction of distal peaks of the projections of the second row, which are arranged facing corresponding projections of the first row, the second row configured to provide further refracted light in a direction of a second base interconnecting the projections in the second row, wherein a corresponding individual one of the projections in the second row includes a planar surface that is configured to receive a sub-aperture portion of the light beam from a corresponding individual one of the sub-aperture refractive elements in the first row, further adjust an angle of the received corresponding sub-aperture portion of the light beam, and counteract a decrease in the size of the corresponding sub-aperture portion of the light beam caused by the individual one of the sub-aperture refractive elements in the first row. 
 
     
     
       2. The apparatus of  claim 1 , wherein the facing corresponding projections respectively include:
 facing corresponding slanted first faces forming an obtuse angle with respect to each other, and slanted with respect to their respective first and second bases; and 
 facing corresponding perpendicular second faces, aligned with respect to each other, and perpendicular to their respective first and second bases. 
 
     
     
       3. The apparatus of  claim 1 , wherein an individual one of the projections in the first row includes a first refractive surface having a first orientation and a corresponding individual one of the projections in the second row include a second refractive surface having a second orientation, wherein the first refractive surface and the second refractive surface have the same shape and the first orientation is opposite to the second orientation. 
     
     
       4. The apparatus of  claim 1 , wherein an individual one of the projections in the first row is shaped such that a difference in an optical path length between an adjacent portion of the individual one of the projections and an adjacent portion of a neighboring projection is an integer number of wavelengths of the light beam. 
     
     
       5. The apparatus of  claim 1  comprising successive first and second rows of projections, wherein the distal peaks of a successive first row face the distal peaks of a corresponding successive second row. 
     
     
       6. The apparatus of  claim 1 , comprising:
 a waveguide core shaped to guide the light beam along a length of a waveguide; 
 a cladding including an electro-optic material capable of an interaction with a portion of the light beam; and 
 at least one electrode shaped and arranged to adjust an angle of the light beam in an in-plane direction by adjusting an index of refraction of the electro-optic material. 
 
     
     
       7. The apparatus of  claim 6 , comprising a row of compensation electrodes shaped and arranged to provide an adjustable phase shift between adjacent sub-aperture portions of the guided light beam to reduce phase discontinuities in adjacent sub-aperture portions of the light beam. 
     
     
       8. The apparatus of  claim 1  wherein the second row of projections is tilted with respect to the first row of projections to accommodate light refracted by the first row of projections. 
     
     
       9. A waveguide for adjusting an angle of a light beam in an in-plane direction, the waveguide comprising:
 a waveguide core shaped to guide a light beam along a length of the waveguide; 
 a cladding including an electro-optic material capable of an interaction with a portion of the light beam; 
 electrodes shaped and arranged to adjust an angle of the light beam in an in-plane direction by adjusting an index of refraction of the electro-optic material, wherein the arrangement of electrodes includes: 
 a first row of projections interconnected by a first base and including a planar surface configured to adjust an angle of corresponding sub-aperture portions of the light beam and decrease a size of the corresponding sub-aperture portions of the light beam by adjusting an index of refraction of the corresponding electro-optic material; and 
 a second row of projections interconnected by a second base and including a planar surface configured to further adjust an angle of corresponding sub-aperture portions of the light beam and counteract a decrease in the size of the corresponding sub-aperture portions of the light beam caused by the first row of projections by adjusting an index of refraction of the corresponding electro-optic material. 
 
     
     
       10. The waveguide of  claim 9 , wherein an individual one of the projections in the first row includes a first shape having a first orientation and a corresponding individual one of the projections in the second row includes a second shape having a second orientation, wherein the first shape and the second shape are the same and the first orientation is opposite to the second orientation. 
     
     
       11. The waveguide of  claim 9 , wherein an individual one of projections in the first row and a corresponding individual one of the projections in the second row have a triangular shape. 
     
     
       12. The waveguide of  claim 9 , wherein an individual one of the projections in the first row is capable of adjusting an angle of the light beam by an angle in the range of zero to two degrees. 
     
     
       13. The waveguide of  claim 9 , wherein an individual one of the projections in the first row is shaped such that a difference in an optical path length between an adjacent portion of a corresponding region of the electro-optic material and a corresponding portion of electro-optic material corresponding to a neighboring projection is an integer number of wavelengths of the light beam when a full steering voltage or zero voltage is applied to the first row of projections to provide a uniform output wavefront. 
     
     
       14. The waveguide of  claim 9 , wherein the arrangement of electrodes includes a row of phase compensation electrodes shaped to provide an adjustable phase shift between adjacent sub-aperture portions of the guided light beam to reduce phase discontinuities in adjacent portions of the light beam at intermediate steering voltages. 
     
     
       15. The waveguide of  claim 9  comprising successive first and second rows of projections, wherein the distal peaks of a successive first row face the distal peaks of a corresponding successive second row. 
     
     
       16. The waveguide of  claim 9  wherein an individual one of projections in the first row and a corresponding individual one of the projections in the second row have a wedge shape. 
     
     
       17. A method of using an arrangement of sub-aperture refractive tapered projections for adjusting an angle of a light beam with reduced diffractive losses, the method comprising:
 receiving light at a first base interconnecting projections in a first row, and providing via planar surfaces, refracted light toward a direction of distal peaks of the projections of the first row; 
 receiving light from a direction of distal peaks of projections of a second row, which are arranged facing corresponding projections of the first row and, using the second row, providing via planar surfaces, further refracted light in a direction of a second base interconnecting the projections in the second row; 
 providing a first electrode shaped to provide the base and projections in the first row by adjusting an index of refraction of a corresponding portion of an electro-optic material in a cladding of a waveguide and a second electrode shaped to provide the base and projections in the second row by adjusting an index of refraction of a corresponding portion of the electro-optic material in the cladding of the waveguide; and 
 applying a full steering voltage to the first electrode to cause corresponding sub-aperture portions of the light beam to decrease in size to provide a separation between adjacent sub-aperture portions of the light beam, and applying an intermediate steering or full steering voltage to the second electrode to counteract the decrease in the size of the corresponding sub-aperture portions of the light beam to reduce the separation between adjacent sub-aperture portions of the light beam. 
 
     
     
       18. The method of  claim 17 , comprising providing a first electrode shaped to provide the base and projections in the first row and a second electrode shaped to provide the base and projections in the second row, the first electrode and the second electrode having the same shape and an opposite orientation. 
     
     
       19. The method of  claim 17 , comprising providing a first electrode shaped to provide the base and projections in the first row and a second electrode shaped to provide the base and projections in the second row, wherein the projections in the first row and the projections in the second row have a triangular shape. 
     
     
       20. The method of  claim 17  wherein the first electrode is shaped to provide the base and projections in the first row by decreasing the index of refraction of a corresponding portion of the electro-optic material in the cladding of the waveguide and the second electrode is shaped to provide the base and projections in the second row by decreasing the index of refraction of a corresponding portion of the electro-optic material in the cladding of the waveguide. 
     
     
       21. The method of  claim 17  wherein an individual one of the projections in the first row is shaped such that a difference in an optical path length between an adjacent portion of a corresponding region of the electro-optic material and a corresponding portion of the electro-optic material corresponding to a neighboring projection is an integer number of wavelengths of the light beam when the full steering voltage or a zero voltage is applied to the first electrode to provide a uniform output wavefront. 
     
     
       22. The method of  claim 17  comprising providing a row of phase compensation electrodes shaped to provide an adjustable phase shift between adjacent sub-aperture portions of the guided light beam to reduce phase discontinuities in adjacent portions of the light beam at intermediate steering voltages. 
     
     
       23. The method of  claim 17  comprising providing a first electrode shaped to provide the base and projections in the first row and a second electrode shaped to provide the base and projections in the second row, wherein the projections in the first row and the projections in the second row have a wedge shape.